Disk fan



July 23, 1929.

M. R. ROBINSON DISK FAN Filed June 5, 1924 Patented July 23, 1929.

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MAYES R. ROBINSON, 0F PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO ROBINSON VEN- TILATING COMPANY, OF ZELIENOIPLE, PENNSYLVANIA, A CORPORATION OF PENN- SYLVANIA.

DISK FAN.

Application filed June 5, 1924. Ser'ial No. 717,990.

This invention is for a disk fan of a new and improved construction.

It is customary in the manufacture of disk fans designed to work against an air pressure to overlap the blades to prevent back flow. This does not efiiciently effect the purpose and unnecessarily restricts the air space between the blades of thefan, cutting down the maximum volume of a1r which the fan may handle, and necessitating such disposition of the blades as to cause power losses by the blades or a portion of them hitting the air with a full fiat surface Furthermore, disk fans as now generally constructed have blades of suchdesign that the air is forced away from the fan in divergentv paths, so that the air strikes the casing or conduit immediately at a point in close proximity to the fan, causing power losses and decrease of the mechanical efficiency of the fan.

Fans of this type are largely used in mining operations and in forced draft boiler installations. It has heretofore been considered impractical to develop a disk or propeller fan that will consistently establish and work against a pressure exceeding one inch of water without the fan soon being torn to pieces, and without low mechanical efficiency. 1 I

In the disk type of fan, it is true that the velocity of the air approaches zero as it nears the center of the wheel, while the maximum velocity is attained at the periphery. Consequently, there is a tendency of the air, when being forced through the easing against any appreciable resistance, to establish a ,back flow in and around the cen-' tral part of the fan. As before stated, attempts have been made to avoid this by overlapping the fan blades, but, due to'the low velocities maintaining or roduced at the center portion of the fan, t iis overlapping of the blades does not avoid the difficulty.

I have found, from extensive experiments,

7 that\the central area of 'a disk fan coveringabout one-fifth or twenty percent of the area of the circle-described by the periphery of the fan, is practically non-productive, and it is through this portion of the area of the wheel that back flow ordinarily occurs. Substantially this percentage holds true irrespective of the diameter of the fan.

How, and any air that should flow in the reverse direction 1s deflected by said central portion into the zone of air high velocity.

A further object of the invention is to provide a fan having the blades thereof so currents of shaped as to cut through the air and project it forwardly with as little shock and friction as possible, and which will direct the air straight forward or in convergentpaths, instead of in divergent paths, so that the a1r does not impinge against the casing close to the fan. The blades, furthermore, are so shaped as to impart a centrifugal or spiral motion to the current'of air which it produces, further reducing frictional losses and increasing the efficiency of the fan. 7 p

The invention maybe understood by reference to the accompanying drawings, in which:

Fig. 1 shows a front view of an eightblade fan involving my invention;

- Fig. 2 is a transverse section in the plane of line II-II of Fig. l;

Fig. 3' is a front view of a four-blade fan; Fig. 4 is a side view, showing the fan pow sitioned in a casing; and

F ig, 5 is a section on line VV of Fig.

3, "showing the true curvature of the blades. The fan may be made as an integral cast- ,ing, as shown in Fig. 1, or it can have, separate blades riveted or otherwise attached in place, as shown in Fig. 3. v

In the drawing, 5 designates a central disk having blades 6 carried thereby. In the center of the disk is a conical hub memher 7, the center of the disk and the hub being perforated for mounting ,on a'suitable shaft, as shaft 9 in Fig. 4. Y

The area of the central disk is in all cases equal to substantially one-fifth or twenty Each blade is separated from the other, so that there is no overlapping ofthe blades at any point. One surface of the fan wheel where the high peripheral speed puts a is substantially flat, the rear surfaces of the blades 'lying as closely as possible in the same plane as the. disk. The entering or.

forward edge of each blade, therefore, lies in the same plane as the disk throughout its length, presenting a thin edge to the air as it rotates. That portion of the forward part of the blade which is disposed in front of a diagonal line drawn from the forward tip of the blade'to the rearmost edge at its point ofjuncture with the disk, is substantially fiat. Such a line'is indicated in Fig.

1 as w'a, and the flat area is designated 6. The remaining area 6 of each blade is gradually and uniformly curved, the pitch or than at divergent lines.

rent of air from the fan is formed into a the radii of curvature at any point being at substantially right angles to the line aa, as. indicated by lines 6-42 of Fig. 1, and line V-V of'Fig. 3. In other words, the curvature is such that any line, such as 0-c,

drawn parallel to any axis of curvature will be substantially parallel with line aa,' and substantially any partof the curved portion of the blade has a slight pitch to- I ward the center of the wheel. i

The shape of the blades is important, and has been determined after a careful observation and experiments based on fans heretofore made.

Presenting, as they do, a thin edge to the air, the blades fslice the air instead of slapping it, as do fans having the entire area of the blade presentedat an angle to the direction of rotation. The gradual curvature of the blades converts the direction of flow of the air easily forward, with minimum friction. The slight pitch" toward the center tends to force the air for ward in slightly convergent lines, rather That is, the curcone. The same pitch toward the center imparts a centripetal motion to the blast of air,.so that the current of air leaving the fan' hasxa spiral movement in thedirection of rotation of the fan. 7

The central disk closes thenon-productive area of the fan, and anyback flow of air is easily diverted by the central cone with a minimum friction out into an air current of sufliciently high velocity to prevent the airfrom flowing back through the fan.

The mechanical efficiency and the volumetric capacity of the fan are greatly increased by the shape of the blade, and the fan can work against higher pressures by reason of the successful elimination of back There is an additional mechanical advantage provided by the construction, and that is that, due to the relatively large diameter of the disk 5, the length of the blade proecting beyond the point of support is greatly reduced, and the blade is supported strain upon the blade. The wheels are thus much stronger and the blades are capable of withstanding high speeds and a relatively great back pressure without any risk of the wheel being torn to pieces.

, In commercial installations, it h'as been found that the fan will have a much greater volumetric capacity than other fans now on the market, and will successfully develop and maintain a pressure of more than two inches of water gauge, as compared with one inch, heretofore considered the limit.

In actual commercial operations, applicants fan has produced fifty percent more air thamthe standard fans of the same size which it replaced, and while running at the same speed,.with only an increase of about thirty-three percentin applied horsepower, with the water gauge showing more than twice as much pressure, all other conditions being the same.

In the drawings, I have shown both an'.

ticular manner of mounting them on the disk 5. v

I claim as my invention: I

1. A disk fan COIIIPIlSlIlg a central disk,

a plurality of blades carried by the disk and extending radially therefrom, each blade having auniformly curved portion with the radii of curvature at any point being sub-.

stantially at right angles to a line drawn from'the forward tip of the blade to the rearmost edge of its point of juncture with the disk, the 'area of the disk being equal to substantially twenty percent of the area of a circle whose-radius is the over-all radius of the wheel.

2. A disk fancomprising a central disk,

a plurality of blades carried by the disk and radiating therefrom, each blade havin a uniformly curved portion with the radii of.

curvature at any point being substantially at right angles to aline drawh from the forward tip of .the blade to ,the rearmost edge of its point of juncture with the disk, said diskhaving an area substantially equal to but not substantially exceeding twenty percent of the area of the circle described by the outer ends of the blades when the fan is rotated. I 7

3. .A disk fan comprising a central disk, a plurality of blades carried by the disk and radiating therefrom, each blade having a I uniformly "curved portion with the radii of curvature at any point being substantially at ward tip of the blade to the rearmost edge of its 'point of juncture with the disk, said disk having an area substantially equalto but not substantially exceeding twenty percent of the area of the circle described by the outer ends of the blades when the fan is rotated, said disk having a central deflecting cone on the pressure side of the fan, said blades being so spaced that they are free of overlapping portions.

4. A disk fan comprising a central disk, a plurality of blades carried'thereby having spaced apart unconnected outer ends, each blade having its forward edge disposed edgewise to the direction of rotation of the wheel, each blade having a fiat surface which increases in widt 1 from the forward tip of the blade to its point of attachment with the disk, the remaining area of the blade being uniformly curved, with the radii of curvature at any point being at substantially right angles to aline drawn from the forward tip of the blade to the rearmost edge of its point of'juncture with the disk.

' 5. A disk fan comprising a central disk, a plurality of blades carried thereby, each blade being wider at its outer end than at its point of juncture with the disk, the forward edge of each blade being disposed edgewise to the direction of rotation of the fan, the area of each blade disposed forwardly of a diagonal line drawn from the forward outer tip of the blade to the rear edgeat substantially the point of attachment with the disk being flat, the remaining larger area of the blade being curved, the curvature being such'that any line drawn through the curved part substantially parallel with said diagonal line between the fiat and curved parts will be parallel with the axis of curvature of the blade, whereby the curved portion of each blade has a slight pitch toward the center of the wheel.

6. A disk fan comprising a central sup-' porting disk member; a plurality of blades carried thereby, each blade wider at its outer .end than at its point of juncture with the disk, the forward edge of each blade being turned toward the direction of rotation of the wheel, the rear portion of each blade being forwardly curved, the curvature being such that the radius of curvature at any point will be at an angle other thana right angle with the forward edge of the blade, the axis of curvature alongany point of the curved area of the blade being substantially parallel with any other axis.

7. A disk fan comprising a central disk, a plurality of blades carried thereby, each blade having its forward edge disposed in the direction of rotation of the disk, each blade being curved, with the curvature having a slight pitch toward the center of the wheel to direct the air in convergent lines forwardly from the wheel.

v8. A disk fan comprising a central disk, a plurality of blades carried thereby and projecting outwardly therefrom, each blade having its forward edge disposed in the direction of rotation of the wheel, the blades being wider at their outer ends than at their point of juncture with the disk, the portion of the blade disposed forwardly of a diagonal line extending from the forward tip of the blade to the rear edge at substantially its point of juncture with the disk being fiat, substantially the entire remaining area of each blade being curved about an axis of curvature lying parallel with said diagonal line, whereby air currents are directed in convergent lines to the front of the fan, said disk having an area equal to substantially twenty percent of the area of a circle described by the wheel.

In testimony whereof I aflizr my signature.

- MAYES R. ROBINSON. 

